1) In String Theory, there are (theoretically) more than three physical dimensions. Different String theorists come up with different numbers, but 9 is a number that I have seen recently.
At very small scales it may be possible to access one or more of those dimensions. That's where I hoped "4D" was going, that would be cool. But no, it's just BS. Stacking does not create a fourth dimension.
2) It's time to stop referring to feature size in nano meters. The first source I could find with an internet search says that the diameter of a silicon atom is .234 nm, so a 20nm feature woud be about 85 silicon atoms across. A 10nm feature woud be about 43 silicon atoms across. At these scales, it would make more sense to use the number of atoms across than the size in nano meters.